The renewal was six weeks late. That was when the real conversation started.
The Scenario
At Xeinadin Richmond, we regularly work with owner-managed agencies and professional services businesses across Richmond, Twickenham, Teddington, Kingston, and South West London where one strong client relationship has quietly become a structural business risk. The pattern is familiar enough that it has a name: client concentration. This is what it looked like for one of them.
You run a twelve-person communications agency in Twickenham. You have been trading for nine years, and the business has grown steadily, if not always smoothly. Your client roster includes a mix of retained accounts and project work, and the retained income gives you enough predictability to plan a year ahead with some confidence.
One client accounts for just under half of your monthly retained income. They have been with you for six years, the relationship is strong, and the renewal conversations have always been straightforward. Until this one.
The renewal is delayed. Six weeks in, the procurement team at the client’s parent company has become involved, and what was a relationship conversation has become a tender process. Your contact there is apologetic but not in control. You are not panicking, but you are also, for the first time in years, doing the arithmetic on what the business looks like without that contract.
The arithmetic is not comfortable.
At a Glance
- Client profile: Owner-managed communications agency, Twickenham, twelve staff, nine years trading
- Situation: Key client representing 47% of retained income delayed renewal by six weeks due to parent company procurement intervention
- Core issue: Extreme revenue concentration, no formal cashflow modelling, no documented contingency plan
- Cause: Organic client growth without portfolio structure review; strong relationship had masked the underlying dependency
Resolution: Cashflow scenario modelling across three outcomes, retained income diversification plan, pricing review on smaller retained clients, payroll exposure review
Outcome: Contract renewed after nine weeks; restructured retainer pricing on three smaller retained clients; first-stage operating reserve target set and achieved within four months
Why concentration risk is so common in owner-managed agencies
Most agencies do not set out to become dependent on a single client. The dependency develops gradually, over years of deepening relationship, expanding scope, and increasing trust. A client that starts as a modest retained account grows into a flagship engagement. The team working on it grows. The revenue from it begins to anchor the monthly forecast. At no single point does anyone make a deliberate decision to let one relationship come to represent 40 or 50 per cent of the business. It simply becomes the case, and by the time it is noticed, unwinding it without disruption is genuinely difficult.
The pattern is especially common in communications, PR, and marketing agencies, where long-term retained relationships are the commercial backbone of the model. A retained client generates predictable income, requires less selling effort, and over time tends to expand rather than contract. All of those qualities make the relationship valuable. They also make it progressively harder to see the structural risk it represents.
Although this example involves a communications agency, the same pattern appears in design studios, IT consultancies, recruitment firms, architects, marketing agencies, and other professional services businesses across the local area. The sector varies; the dependency dynamic does not.
The warning signs, when they are present at all, are easy to misread.
A slight slowing in the approval of new scope. A change of contact at the client. A restructuring at the parent company. A procurement team appearing in conversations that previously sat with the marketing director. None of these are necessarily alarming in isolation. In combination, and with a client at 47 per cent of retained income, they represent a specific and material risk that deserves explicit attention.
Concentration risk becomes more dangerous when combined with funding pressure, rising costs, slower client decision-making, and a market that is less forgiving of operational fragility. The article Why March 2026 Feels Different for Richmond Business Owners sets out a number of the external pressures currently bearing on owner-managed businesses in the area. Concentration risk does not create itself in a vacuum.
Why the risk is rarely visible until the moment of stress
The particular difficulty with client concentration risk is that it is entirely invisible during normal trading conditions. A business generating strong margins from a flagship client looks healthy by every conventional measure: revenue is up, the team is busy, the bank account behaves predictably. The risk only materialises when the relationship comes under pressure, at which point the business has no preparation time and no fallback.
This is structurally different from most other business risks, which tend to show early warning signals. Cashflow pressure builds over weeks. Margin erosion shows up in the monthly P&L. Staff turnover becomes visible in a rising recruitment cost line. Concentration risk shows nothing until it shows everything.
There is also a psychological dimension to the problem. An agency owner who has built a strong six-year relationship with a client is, understandably, reluctant to regard that relationship as a source of risk. The relationship feels like an asset, and it is an asset. The issue is that the same qualities that make it valuable, depth, trust, informality, also make its disruption acutely destabilising. The stronger the relationship, the more the business has typically been built around it.
“We see this regularly. The agency that has a fantastic flagship client is often in a more fragile position than the agency with five modest ones. The flagship client makes the business look successful. It also means there is very little margin for error if that relationship shifts.”
The article Why 2026 Feels Harder Than It Should for Richmond Businesses addresses the broader context in which these structural vulnerabilities become more consequential. A business that was able to absorb a significant client disruption in a buoyant market may find the same disruption considerably harder to manage when the environment is less forgiving.
How the scenario unfolded
The case described here is drawn from composite client experience. The details reflect patterns we encounter regularly among owner-managed professional services businesses in the Richmond and Twickenham area.
The agency owner had founded the business in 2016 and built it steadily through a combination of referral and reputation. By early 2025, she had a team of twelve, a solid client roster, and what felt like a stable business. The flagship client, a regional division of a larger consumer goods group, had been on a retained basis since 2019 and had expanded its scope twice in that period. The annual retainer value was approximately £312,000, which represented 47 per cent of total retained income.
When the renewal stalled, the first six weeks were spent managing the relationship, staying close to her contact at the client, and waiting for the procurement process to clarify. It was only when a formal tender document arrived, asking her agency to compete alongside two others, that the structural reality became impossible to avoid.
She came to see our business advisory team at that point. Not because she expected to lose the tender, but because she had done the back-of-envelope arithmetic and found she could not clearly answer the question: if we lose this, what does the business look like in month three?
“She was a good operator who had built something real. The issue was not the quality of the business. The issue was that she had never had to think about it from this angle before, because the flagship relationship had always renewed without drama. The tender process was the first time the question had been put to her directly.”
What the process involved
The first piece of work was scenario modelling. We constructed three versions of the business cashflow across the following twelve months: a contract renewal at the existing value, a renewal at a reduced scope (which the tender document implied was possible), and a full loss of the contract. Each scenario was built on the actual cost base, including payroll commitments, lease obligations, software subscriptions, and the owner’s own drawings.
The results were clarifying, if uncomfortable.
For the modelling exercise, we looked at total forecast monthly income, including both retained income and expected project work, against the agency’s current monthly operating cost base of approximately £51,000 per month. The three scenarios looked as follows:
The reduced scope scenario was the one that most needed attention. A business generating a £6,400 monthly surplus on a cost base of £51,000 has essentially no buffer. One difficult month, one unexpected cost, one slower-than-expected payment, and it is in a negative position. The full loss scenario was severe but would require active management regardless of advance preparation; the reduced scope scenario was the trap, because it looked survivable but was not actually sustainable without further action.
The second piece of work was a payroll exposure review. Of the twelve staff, four were directly allocated to the flagship account for the majority of their time. In the event of a significant scope reduction or a full contract loss, the business would need to make decisions about those roles quickly. We mapped the contractual and statutory obligations across those four positions, including notice periods, any enhanced terms in their contracts, and the potential redundancy cost, so that the owner had a clear picture of both the timeline and the financial exposure.
The third piece of work was a pricing review on the smaller retained clients, sometimes called the tail of the client portfolio. Six of the agency’s retained clients were paying rates that had not been reviewed since 2021 or 2022. In several cases the scope of work had expanded informally without a corresponding increase in the retainer value. A structured review of those six relationships, using current market rate benchmarks and a clear articulation of the expanded scope, identified an additional £4,200 per month of recoverable income. That figure did not solve the concentration problem, but it meaningfully improved the reduced-scope scenario and gave the business a more defensible position from which to manage the transition if needed.
What the outcome was
The tender process ran for nine weeks in total. The agency was reappointed, at a retainer value approximately 8 per cent lower than the previous contract, reflecting a modest scope reduction on one workstream that the parent company had decided to bring in-house. The outcome was better than the reduced-scope scenario we had modelled, and the business absorbed the reduction without operational disruption.
But the more significant outcome was structural.
The owner left the process with a clear view of her concentration risk for the first time. The flagship client now represented 43 per cent of retained income rather than 47 per cent, a modest improvement but not a structural solution. We agreed a three-year diversification target: no single client to represent more than 30 per cent of retained income, no two clients combined to represent more than 50 per cent, and no three clients combined to represent more than 60 per cent. Working towards those targets required active new business development rather than the largely passive referral model the business had relied on, and we put a quarterly review against the portfolio metrics in place.
The first-stage cash reserve target, equivalent to one month of total operating costs, was reached within four months. This was achieved partly through the tail client pricing review and partly through a modest reduction in owner drawings during the recovery period. The reserve was held in a separate account and treated as genuinely untouchable except in a defined cashflow emergency. The longer-term aim was to build towards a more resilient two-to-three-month reserve as the portfolio diversified and margins improved.
The article Key Factors Affecting Richmond Businesses and Taxpayers in 2026 addresses the broader commercial landscape in which these structural questions now sit. An agency that has done this work, mapped its concentration risk, modelled the scenarios, and built a cash reserve, is substantially better positioned to navigate the next period of external uncertainty than one that has not.
The three disciplines that prevent concentration risk from becoming a crisis
Looking back across the cases we see in this area, the businesses that manage concentration risk most effectively share three disciplines that others tend to lack.
The first is portfolio measurement. They know, at any point in the year, what each client represents as a percentage of total revenue and of retained income specifically. The number is not calculated in a crisis; it is part of the regular management information the owner looks at quarterly. When it drifts above a threshold, it prompts a conversation, not an emergency.
The second is pricing discipline. The businesses most exposed to concentration risk are often the ones that have allowed their pricing on smaller clients to stagnate, which means the gap between the flagship client and the rest of the portfolio widens over time. A pricing review on tail clients is not just a revenue improvement exercise. It is a structural rebalancing that reduces the relative weight of the flagship without requiring any change in that relationship.
The third is cashflow scenario planning. Not complex financial modelling, but a simple and honest answer to one question: if our largest client gave us notice tomorrow, what would the business look like in ninety days? Owners who can answer that question clearly, and have a plan for it, are in a fundamentally different position from those who cannot.
Frequently asked questions
What is client concentration risk?
Client concentration risk refers to the financial and operational vulnerability that arises when a disproportionate share of a business’s revenue comes from a small number of clients, or a single client. In professional services, a commonly used threshold is that any single client representing more than 25 to 30 per cent of revenue constitutes a material concentration risk. Above 40 per cent, the dependency is significant enough to require explicit management attention and contingency planning.
How much revenue from one client is too much?
There is no universally fixed threshold, but most advisers working with professional services businesses treat 25 to 30 per cent as the point at which a single client relationship moves from being commercially important to being structurally risky. Above 40 per cent, the business is effectively dependent on that relationship continuing. The risk is not that the client will necessarily leave; it is that the business has no meaningful resilience if they do. The percentage should be assessed on retained income separately from total income, because the impact of losing a retained client is usually more immediate than losing project work.
What should I do if my business depends on one major client?
The immediate priority is to understand the scenario clearly: what the business looks like financially if the client reduces scope by half, and what it looks like if the client is lost entirely. Most owners who have not done this calculation find it clarifying rather than alarming, because the actual exposure is usually more manageable than the imagined version. From there, the practical response involves three parallel workstreams: building a cash reserve that buys time in a disruption, reviewing pricing on smaller clients to improve margin without adding new business risk, and beginning active new business development targeted at the client types that can reduce the flagship’s relative weight.
How do I calculate my own client concentration risk?
The basic calculation is straightforward: divide each client’s annual revenue by total annual revenue and express it as a percentage. Do this for retained income separately from project income, because the dependency on retained income is structurally more significant. Once you have the percentages, map them against a threshold of your choosing, typically 25 to 30 per cent for a single client, and identify any relationships that sit above it. The calculation takes less than an hour and is worth repeating quarterly.
How can an agency survive losing its biggest client?
Survival depends on three things: the cash position at the point of loss, the flexibility of the cost base, and the speed at which the pipeline can be activated. An agency with one month of operating costs in reserve, a cost base that includes some variable elements, and an active new business programme has a meaningfully different outlook from one with no reserve, a fully fixed cost base, and a purely referral-dependent pipeline. None of those positions is achieved overnight, which is why the planning is most valuable when it happens before the relationship shows any sign of strain.
What is a realistic cash reserve target for an agency?
The most commonly used benchmark is one to three months of total operating costs, held in a separate account that is not used for working capital. For a business with a cost base of £50,000 per month, that means a reserve of between £50,000 and £150,000. The right target depends on the client portfolio structure: a business with high concentration in one or two clients needs a larger reserve than one with ten clients of roughly equal size, because the impact of a single loss is proportionally greater. A first-stage target of one month, building over time towards two or three, is a realistic and achievable approach for most agencies.
What should I do if a key client relationship shows warning signs?
The practical steps are to model the scenario explicitly before it becomes an emergency, review the payroll and contractual obligations for any staff primarily allocated to that client, identify where the tail client pricing has drifted and what recovery is possible, and begin new business development activity even if the relationship appears to be recovering. Acting before the outcome is known is almost always less disruptive than acting after it is confirmed.
Is it reasonable to pass cost increases on to long-standing retained clients?
Yes, and most long-standing clients expect it. A retained relationship that has not been repriced since 2021 or 2022 has effectively been receiving a real-terms discount for three or more years, given the rate of cost inflation over that period. A structured repricing conversation, framed around expanded scope, market rate benchmarks, and the value the relationship has delivered, is a normal part of a professional services relationship. Clients who react badly to a reasonable repricing conversation are also telling you something useful about the relationship.
What diversification target should an agency set?
A reasonable target is that no single client represents more than 25 to 30 per cent of retained income, no two clients combined represent more than 50 per cent, and no three clients combined represent more than 60 per cent. These thresholds are not fixed rules, but they reflect a portfolio structure where the loss of any one relationship, however significant, does not threaten the viability of the business. Getting there from a position of high concentration is a multi-year process; the value is in having the target and measuring against it, not in achieving it immediately.
Can Xeinadin Richmond help with cashflow modelling for agencies?
Yes. Cashflow scenario modelling, management accounts and portfolio analysis are a regular part of what our business advisory team does with owner-managed professional services businesses across the Richmond and Twickenham area. If you have a specific concern about concentration risk or want to understand your cashflow resilience under different scenarios, a short diagnostic conversation is usually the most useful starting point.
How does client concentration risk affect business valuation?
Significantly. A business where a single client represents more than 30 to 40 per cent of revenue will typically be valued at a discount relative to a comparable business with a more diversified client base. Acquirers and investors price the dependency explicitly, because the risk of the concentrated client departing post-acquisition is real and the impact on earnings is material. An agency planning to sell or seek investment in the next three to five years has a commercial incentive, as well as an operational one, to address concentration before the process begins.
If this feels familiar
If you run a professional services or agency business and one client relationship accounts for more than a quarter of your income, the scenario above is worth sitting with. The question is not whether the relationship will renew. It is whether you have done the work to know what happens if it does not.
Our team in Richmond works with owner-managed businesses across the south-west London area. A short conversation about portfolio structure and cashflow resilience costs very little and can change the way you think about a risk you may already be carrying.
About the author
Donovan Crutchfield, ACA – Area Managing Partner, Xeinadin Richmond.
Connect with Donovan on LinkedIn.
Donovan works with owner-managed businesses and private individuals across Richmond-upon-Thames and the wider South West London catchment. His practice includes a significant number of professional services businesses managing the commercial and financial disciplines that come with sustained growth.
This case study is based on composite client experience and does not represent any single individual. All identifying details have been changed. The information provided is for general guidance only and should not be treated as a substitute for professional financial or business advice specific to your circumstances.
